pH-Metric Studies on the Interaction of Ni-Containing Anderson Type Heteropolyanions in Aqueous Solution.

pH-potentiometry and mathematical modeling were used to study interactions in the system $$ {\text{Ni}}^{2 +}{-}{\text{MoO}}_{4}^{2 -}{-}{\text{H}}^{ + } {-}{\text{H}}_{ 2} {\text{O}} $$ acidified to mole ratio $$ Z = \nu ({\text{H}}^{ + } )/\nu \left( {{\text{MoO}}_{4}^{2 - } } \right) = 1.00 $$ , within the acidity interval Z = 0.6-2.5 at 298 ± 0.1 K, with background electrolyte NaNO ( I = 0.1-0.5 mol·dm). Previously unknown thermodynamic constants and Gibbs energies for the formation reactions of Anderson type heteropoly anions H[Ni(OH)MO] (M = Mo, W) from $$ {\text{MoO}}_{4}^{2 - } $$ and H, as well as their standard Gibbs energies of formation $$ \Delta G_{\text{f}}^{0} $$ , were calculated. For the first time, the speciation schemes of the ions in Ni- $$ {\text{MoO}}_{4}^{2 - } $$ -H-HO (M = Mo, W) solutions are proposed. [ABSTRACT FROM AUTHOR]